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Difference between revisions of "cpp/numeric/random/bernoulli distribution"

From cppreference.com
< cpp‎ | numeric‎ | random
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{{cpp/title|bernoulli_distribution}}
 
{{cpp/title|bernoulli_distribution}}
 
{{cpp/numeric/random/bernoulli_distribution/navbar}}
 
{{cpp/numeric/random/bernoulli_distribution/navbar}}
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{{ddcl | header=random | since=c++11 | 1=
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{{ddcl|header=random|since=c++11|1=
 
class bernoulli_distribution;
 
class bernoulli_distribution;
 
}}
 
}}
  
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Produces random boolean values, according to the discrete probability function. The probability of {{c|true}} is  
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Produces random boolean values, according to the discrete probability function. The probability of {{co|true}} is
  
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:{{math|P(b{{!}}p) {{=}}}}{{mparen|{||{{math|p}} if {{c|b {{==}} true }} | {{math|1 − p}} if {{c|b {{==}} false}}|style=text-align:right}}
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:{{math|1=P(b{{!}}p) =}}{{mparen|{||{{math|p}}, if {{math|b}} is {{co|true}}|{{math|1 − p}}, if {{math|b}} is {{co|false}}|style=text-align:right}}
  
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Like all distributions, {{tt|std::bernoulli_distribution}} is {{concept|CopyConstructible}} and {{concept|CopyAssignable}}
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{{tt|std::bernoulli_distribution}} satisfies {{named req|RandomNumberDistribution}}.
  
 
===Member types===
 
===Member types===
 
{{dsc begin}}
 
{{dsc begin}}
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{{dsc hitem | Member type | Definition}}
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{{dsc hitem|Member type|Definition}}
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{{dsc | {{tt|result_type}} | {{c|bool}}}}
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{{dsc|{{tt|result_type}} {{mark c++11}}|{{co|bool}}}}
 
{{cpp/numeric/random/param_type}}
 
{{cpp/numeric/random/param_type}}
 
{{dsc end}}
 
{{dsc end}}
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===Member functions===
 
===Member functions===
 
{{dsc begin}}
 
{{dsc begin}}
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{{dsc inc | cpp/numeric/random/distribution/dsc constructor | bernoulli_distribution}}
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{{dsc inc|cpp/numeric/random/distribution/dsc constructor|bernoulli_distribution}}
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{{dsc inc | cpp/numeric/random/distribution/dsc reset | bernoulli_distribution}}
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{{dsc inc|cpp/numeric/random/distribution/dsc reset|bernoulli_distribution}}
  
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{{dsc h2 | Generation}}
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{{dsc h2|Generation}}
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{{dsc inc | cpp/numeric/random/distribution/dsc operator() | bernoulli_distribution}}
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{{dsc inc|cpp/numeric/random/distribution/dsc operator()|bernoulli_distribution}}
  
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{{dsc h2 | Characteristics}}
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{{dsc h2|Characteristics}}
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{{dsc inc | cpp/numeric/random/bernoulli_distribution/dsc p}}
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{{dsc inc|cpp/numeric/random/bernoulli_distribution/dsc p}}
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{{dsc inc | cpp/numeric/random/distribution/dsc param | bernoulli_distribution}}
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{{dsc inc|cpp/numeric/random/distribution/dsc param|bernoulli_distribution}}
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{{dsc inc | cpp/numeric/random/distribution/dsc min | bernoulli_distribution}}
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{{dsc inc|cpp/numeric/random/distribution/dsc min|bernoulli_distribution}}
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{{dsc inc | cpp/numeric/random/distribution/dsc max | bernoulli_distribution}}
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{{dsc inc|cpp/numeric/random/distribution/dsc max|bernoulli_distribution}}
 
{{dsc end}}
 
{{dsc end}}
  
 
===Non-member functions===
 
===Non-member functions===
 
{{dsc begin}}
 
{{dsc begin}}
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{{dsc inc | cpp/numeric/random/distribution/dsc operator_cmp | bernoulli_distribution }}
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{{dsc inc|cpp/numeric/random/distribution/dsc operator_cmp|bernoulli_distribution}}
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{{dsc inc | cpp/numeric/random/distribution/dsc operator_ltltgtgt | bernoulli_distribution}}
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{{dsc inc|cpp/numeric/random/distribution/dsc operator_ltltgtgt|bernoulli_distribution}}
 
{{dsc end}}
 
{{dsc end}}
  
 
===Example===
 
===Example===
 
{{example
 
{{example
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| code=
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|code=
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#include <iostream>
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#include <iomanip>
 
#include <iomanip>
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#include <string>
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#include <iostream>
 
#include <map>
 
#include <map>
 
#include <random>
 
#include <random>
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#include <string>
  
 
int main()
 
int main()
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     std::map<bool, int> hist;
 
     std::map<bool, int> hist;
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     for(int n=0; n<10000; ++n) {
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     for (int n = 0; n < 10000; ++n)
 
         ++hist[d(gen)];
 
         ++hist[d(gen)];
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     }
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     for(auto p : hist) {
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     std::cout << std::boolalpha;
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         std::cout << std::boolalpha << std::setw(5) << p.first
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     for (auto const& [key, value] : hist)
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                  << ' ' << std::string(p.second/500, '*') << '\n';
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         std::cout << std::setw(5) << key << ' '
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    }
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                  << std::string(value / 500, '*') << '\n';
 
}
 
}
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| output=
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|p=true
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|output=
 
false ***************
 
false ***************
 
  true ****
 
  true ****
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===External links===
 
===External links===
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[http://mathworld.wolfram.com/BernoulliDistribution.html Weisstein, Eric W. "Bernoulli Distribution."] From MathWorld--A Wolfram Web Resource.
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{{eli|[https://mathworld.wolfram.com/BernoulliDistribution.html Weisstein, Eric W. "Bernoulli Distribution."] From MathWorld &mdash; A Wolfram Web Resource.}}
  
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[[de:cpp/numeric/random/bernoulli distribution]]
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{{langlinks|de|es|fr|it|ja|pt|ru|zh}}
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Latest revision as of 23:26, 16 October 2023

 
C++
 
Numerics library
Common mathematical functions
Mathematical special functions (C++17)
Mathematical constants (C++20)
Basic linear algebra algorithms (C++26)
Floating-point environment (C++11)
Complex numbers
Numeric array (valarray)
Pseudo-random number generation
Factor operations
(C++17)
(C++17)
Interpolations
(C++20)
(C++20)
Saturation arithmetic
(C++26)
(C++26)
(C++26)
(C++26)
(C++26)

Generic numeric operations
Bit operations
(C++20)    
(C++20)
(C++20)
(C++20)
(C++20)
(C++20)
(C++20)
(C++20)
(C++20)
(C++20)
(C++20)
(C++20)
(C++23)
(C++20)
 
Pseudo-random number generation
 
std::bernoulli_distribution
 
Defined in header <random>
class bernoulli_distribution;
 (since C++11)

Produces random boolean values, according to the discrete probability function. The probability of true is

P(b|p) =⎧
⎨
⎩p, if b is true
1 − p, if b is false

std::bernoulli_distribution satisfies RandomNumberDistribution.

Contents

[edit] Member types

Member type Definition
result_type (C++11) bool
param_type (C++11) the type of the parameter set, see RandomNumberDistribution.

[edit] Member functions

(C++11)
 constructs new distribution
(public member function) [edit]
(C++11)
 resets the internal state of the distribution
(public member function) [edit]
Generation
(C++11)
 generates the next random number in the distribution
(public member function) [edit]
Characteristics
(C++11)
 returns the p distribution parameter (probability of generating true)
(public member function) [edit]
(C++11)
 gets or sets the distribution parameter object
(public member function) [edit]
(C++11)
 returns the minimum potentially generated value
(public member function) [edit]
(C++11)
 returns the maximum potentially generated value
(public member function) [edit]

[edit] Non-member functions

(C++11)(C++11)(removed in C++20)
 compares two distribution objects
(function) [edit]
(C++11)
 performs stream input and output on pseudo-random number distribution
(function template) [edit]

[edit] Example

Run this code
#include <iomanip>
#include <iostream>
#include <map>
#include <random>
#include <string>
 
int main()
{
    std::random_device rd;
    std::mt19937 gen(rd());
    // give "true" 1/4 of the time
    // give "false" 3/4 of the time
    std::bernoulli_distribution d(0.25);
 
    std::map<bool, int> hist;
    for (int n = 0; n < 10000; ++n)
        ++hist[d(gen)];
 
    std::cout << std::boolalpha;
    for (auto const& [key, value] : hist)
        std::cout << std::setw(5) << key << ' '
                  << std::string(value / 500, '*') << '\n';
}

Possible output: 

false ***************
 true ****

[edit] External links

Weisstein, Eric W. "Bernoulli Distribution." From MathWorld — A Wolfram Web Resource.
Retrieved from "https://en.cppreference.com/mwiki/index.php?title=cpp/numeric/random/bernoulli_distribution&oldid=160787"